8-33 (FeNH 4 (SO 4 ) 2 .12H 2 O) dissolved in 0.15 mL of 0.1 M HCl to 400 μg of CT dissolved in 1 mL of 68% aqueous methanol. (ii) Ascorbic acid concentrations in the final sample/reagent matrix of 0-400 μg mL -1 prepared in 1 mL of 68% aqueous methanol, containing 400 μg of CT. (iii) Sodium metabisulphite (Na 2 S 2 O 5 ) concentrations of 0-263 μg mL in the final sample/reagent matrix, prepare...